There are emission control systems presently in use which recover vapors generated during normal operating conditions. Fuel agitation, heating and expansion necessitate that the tank be vented to insure reasonable pressure limits. In the known systems the vented vapors are either fed directly to the engine or are first stored in a storage container and then later withdrawn from the container and fed to the engine.
Others have investigated ways of recovering vapor during a refueling operation. Example systems are disclosed in SAE Technical Paper Series, No. 861551, by W.J. Koehl, D. W. Lloyd and L. J. McCabe, entitled "Vehicle Onboard Control of Refueling Emissions - System Demonstration on a 1985 Vehicle"; and in SAE Technical Paper Series, No. 861560, by George S. Musser and Hugh F. Shannon, entitled "Onboard Control of Refueling Emissions." It has also been proposed that a sensor be positioned adjacent a door positioned over a closure cap on a fuel fill tube leading into a fuel tank. The sensor senses the opening of the door and connects a source of vacuum to a valve in a vent line, causing the valve to open and allow the flow of vapor from the fuel tank to a storage container.
A principal object of the present invention is to provide an onboard vapor recovery system which is operable during refueling and which is extremely simple and does not require the use of door sensors, a source of vacuum, etc.
The vapor recovery systems of the invention are combinable with the aforementioned emission control systems which recover vapors during normal operating conditions.
The vapor recovery systems of the invention may (and preferably do) utilize vapor/liquid discriminators and normal vent/rollover valves of a type covered by U.S. Pat. No. 4,325,398, granted Apr. 20, 1982, and entitled Safety and Venting Valves for Fuel Tanks Carried on Vehicles; by U.S. Pat. No. 4,457,325, granted July 3, 1984, and entitled Safety and Venting Cap for Vehicle Fuel Tanks; and by U.S. Pat. No. 4,487,215, granted Dec. 11, 1984, and entitled Gas Venting Valve.
The vapor recovery systems of the invention are characterized by extreme simplicity. Each comprises a small number of inexpensive and highly reliable components. The systems preferably involve a modular design resulting in an ease of installation and lower production costs. The systems are easily adaptable to existing fuel tank systems on vehicles. The necessary modifications to the existing tank components are minimal. There is no interference with the operation of the automatic shut-off systems which are a part of most refueling systems in use today.